在React Native跨平台技术在开源鸿蒙中实现最长递减子序列(Longest Decreasing Subsequence, LDS)算法,并计算它们的最长递减子序列的长度
本文介绍了在React Native中实现最长递减子序列(LDS)算法的动态规划方法。通过创建一个JavaScript函数计算数组的LDS长度,并将其集成到React Native组件中展示结果。文章提供了完整的代码示例,包括动态规划算法实现、React Native组件开发以及应用运行方法。该方案采用动态规划的时间复杂度为O(n²),适用于处理中等规模数据,并可通过输入框接收用户输入的数字序列进
在React Native中实现最长递减子序列(Longest Decreasing Subsequence, LDS)算法,你可以选择使用原生JavaScript来实现这一算法,然后将结果展示在React Native的UI组件中。最长递减子序列问题是动态规划的一个常见应用,可以通过多种方法解决,例如递归、动态规划等。下面我将介绍如何使用动态规划方法来实现这一算法,并在React Native中展示结果。
- 动态规划实现LDS
首先,我们需要一个函数来计算一个数组的最长递减子序列。
function longestDecreasingSubsequence(arr) {
if (arr.length === 0) return 0;
const n = arr.length;
let dp = new Array(n).fill(1); // 初始化dp数组,每个元素至少为1
for (let i = 1; i < n; i++) {
for (let j = 0; j < i; j++) {
if (arr[i] < arr[j]) {
dp[i] = Math.max(dp[i], dp[j] + 1);
}
}
}
return Math.max(...dp); // 返回dp数组中的最大值
}
- 在React Native中展示结果
接下来,我们创建一个React Native组件来使用这个函数并展示结果。
import React, { useState } from 'react';
import { View, Text, Button, TextInput } from 'react-native';
const LDSComponent = () => {
const [input, setInput] = useState('');
const [result, setResult] = useState('');
const handleCalculate = () => {
const arr = input.split(',').map(Number); // 将输入字符串转换为数字数组
const length = longestDecreasingSubsequence(arr);
setResult(`The length of the longest decreasing subsequence is: ${length}`);
};
return (
<View style={{ padding: 20 }}>
<TextInput
style={{ height: 40, borderColor: 'gray', borderWidth: 1, marginBottom: 10 }}
onChangeText={text => setInput(text)}
value={input}
placeholder="Enter numbers separated by commas"
keyboardType="numeric"
/>
<Button title="Calculate LDS" onPress={handleCalculate} />
<Text>{result}</Text>
</View>
);
};
export default LDSComponent;
- 运行你的React Native应用
确保你已经安装了React Native环境,并且可以通过以下命令启动你的应用:
npx react-native run-Harmony 对于Harmony平台
npx react-native run-Harmony 对于Harmony平台
- 使用组件
在你的应用中使用LDSComponent组件,例如在App.js中:
import React from 'react';
import { View } from 'react-native';
import LDSComponent from './LDSComponent'; // 确保路径正确
const App = () => {
return (
<View style={{ flex: 1, justifyContent: 'center', alignItems: 'center' }}>
<LDSComponent />
</View>
);
};
export default App;
这样,你就可以在React Native应用中输入一系列数字,并计算它们的最长递减子序列的长度了。
真实代码演示:
// app.tsx
import React, { useState } from 'react';
import { SafeAreaView, View, Text, StyleSheet, TouchableOpacity, ScrollView, Modal } from 'react-native';
// Base64 图标库
const ICONS = {
play: 'PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHZpZXdCb3g9IjAgMCAyNCAyNCIgZmlsbD0id2hpdGUiPjxwYXRoIGQ9Ik04IDV2MTRsMTEtN3oiLz48L3N2Zz4=',
refresh: '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',
info: 'PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHZpZXdCb3g9IjAgMCAyNCAyNCIgZmlsbD0id2hpdGUiPjxwYXRoIGQ9Ik0xMiAyQzYuNDcgMiAyIDYuNDcgMiAxMnM0LjQ3IDEwIDEwIDEwIDEwLTQuNDcgMTAtMTBTMTcuNTMgMiAxMiAyem0xIDE1aC0ydjJoMnYtMnptMC02aC0ydjVoMnYtNXoiLz48L3N2Zz4=',
chart: 'PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHZpZXdCb3g9IjAgMCAyNCAyNCIgZmlsbD0id2hpdGUiPjxwYXRoIGQ9Ik0zIDEzdi0yYzAtLjU1LjQ1LTEgMS0xaDZjLjU1IDAgMSAuNDUgMSAxdjJjMCAuNTUtLjQ1IDEtMSAxaC02Yy0uNTUgMC0xLS40NS0xLTF6bTEyIDB2LTJjMC0uNTUuNDUtMSAxLTFoNmMuNTUgMCAxIC40NSAxIDF2MmMwIC41NS0uNDUgMS0xIDFoLTZjLS41NSAwLTEtLjQ1LTEtMXptLTYtN3YyYzAgLjU1LS40NSAxLTEgMWgtNmMtLjU1IDAtMS0uNDUtMS0xVjZjMC0uNTUuNDUtMSAxLTFoNmMuNTUgMCAxIC40NSAxIDF6Ii8+PC9zdmc+',
close: 'PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHZpZXdCb3g9IjAgMCAyNCAyNCIgZmlsbD0id2hpdGUiPjxwYXRoIGQ9Ik0xOSA2LjQxTDE3LjU5IDUgMTIgMTAuNTkgNi40MSA1IDUgNi40MSAxMC41OSAxMiA1IDE3LjU5IDYuNDEgMTkgMTIgMTMuNDEgMTcuNTkgMTkgMTkgMTcuNTkgMTMuNDEgMTJ6Ii8+PC9zdmc+'
};
// 默认测试数据
const DEFAULT_SEQUENCES = [
{ id: 1, name: '示例序列 1', data: [9, 5, 7, 3, 8, 2, 6, 1] },
{ id: 2, name: '示例序列 2', data: [10, 9, 8, 7, 6, 5, 4, 3, 2, 1] },
{ id: 3, name: '示例序列 3', data: [1, 2, 3, 4, 5, 6, 7, 8, 9] },
{ id: 4, name: '示例序列 4', data: [5, 3, 4, 2, 6, 1, 8, 7] }
];
// LDS算法实现
const ldsAlgorithms = {
// 动态规划方法 O(n^2)
dpMethod: (arr: number[]): { length: number; sequence: number[] } => {
const n = arr.length;
if (n === 0) return { length: 0, sequence: [] };
const dp = new Array(n).fill(1);
const parent = new Array(n).fill(-1);
for (let i = 1; i < n; i++) {
for (let j = 0; j < i; j++) {
if (arr[j] > arr[i] && dp[j] + 1 > dp[i]) {
dp[i] = dp[j] + 1;
parent[i] = j;
}
}
}
let maxLength = dp[0];
let maxIndex = 0;
for (let i = 1; i < n; i++) {
if (dp[i] > maxLength) {
maxLength = dp[i];
maxIndex = i;
}
}
// 构造最长递减子序列
const result = [];
let current = maxIndex;
while (current !== -1) {
result.unshift(arr[current]);
current = parent[current];
}
return { length: maxLength, sequence: result };
},
// 二分查找优化方法 O(n log n)
binarySearchMethod: (arr: number[]): { length: number; sequence: number[] } => {
const n = arr.length;
if (n === 0) return { length: 0, sequence: [] };
const tails = [];
const predecessors = new Array(n).fill(-1);
const indices = [];
for (let i = 0; i < n; i++) {
let left = 0;
let right = tails.length;
while (left < right) {
const mid = Math.floor((left + right) / 2);
if (tails[mid] > arr[i]) {
left = mid + 1;
} else {
right = mid;
}
}
if (left === tails.length) {
tails.push(arr[i]);
indices.push(i);
} else {
tails[left] = arr[i];
indices[left] = i;
}
if (left > 0) {
predecessors[i] = indices[left - 1];
}
}
// 构造最长递减子序列
const result = [];
let current = indices[indices.length - 1];
while (current !== -1) {
result.unshift(arr[current]);
current = predecessors[current];
}
return { length: tails.length, sequence: result };
}
};
const LDSComparison: React.FC = () => {
const [sequences] = useState(DEFAULT_SEQUENCES);
const [selectedSequence, setSelectedSequence] = useState<any>(null);
const [results, setResults] = useState<any>(null);
const [modalVisible, setModalVisible] = useState(false);
const [infoModalVisible, setInfoModalVisible] = useState(false);
// 运行算法对比
const runComparison = (sequence: any) => {
setSelectedSequence(sequence);
const dpResult = ldsAlgorithms.dpMethod(sequence.data);
const binaryResult = ldsAlgorithms.binarySearchMethod(sequence.data);
setResults({
dp: dpResult,
binary: binaryResult
});
setModalVisible(true);
};
// 渲染SVG图标
const renderSvgIcon = (base64Icon: string, style: any) => {
return (
<Text style={[styles.svgIcon, style]}>
{String.fromCharCode(...atob(base64Icon).split('').map(char => char.charCodeAt(0)))}
</Text>
);
};
return (
<SafeAreaView style={styles.container}>
<View style={styles.header}>
<Text style={styles.title}>📉 LDS算法对比</Text>
<Text style={styles.subtitle}>最长递减子序列算法性能分析</Text>
<TouchableOpacity
style={styles.infoButton}
onPress={() => setInfoModalVisible(true)}
>
{renderSvgIcon(ICONS.info, styles.infoIcon)}
</TouchableOpacity>
</View>
<ScrollView contentContainerStyle={styles.content}>
<View style={styles.sequenceList}>
{sequences.map((sequence) => (
<View key={sequence.id} style={styles.sequenceCard}>
<View style={styles.sequenceHeader}>
<Text style={styles.sequenceName}>{sequence.name}</Text>
<Text style={styles.sequenceLength}>长度: {sequence.data.length}</Text>
</View>
<View style={styles.sequenceData}>
<Text style={styles.sequenceText}>
[{sequence.data.join(', ')}]
</Text>
</View>
<TouchableOpacity
style={styles.runButton}
onPress={() => runComparison(sequence)}
>
{renderSvgIcon(ICONS.play, styles.playIcon)}
<Text style={styles.runButtonText}>运行对比</Text>
</TouchableOpacity>
</View>
))}
</View>
</ScrollView>
{/* 算法对比结果模态框 */}
<Modal
animationType="slide"
transparent={true}
visible={modalVisible}
onRequestClose={() => setModalVisible(false)}
>
<View style={styles.modalOverlay}>
<View style={styles.modalContent}>
<View style={styles.modalHeader}>
<Text style={styles.modalTitle}>算法对比结果</Text>
<TouchableOpacity onPress={() => setModalVisible(false)}>
<Text style={styles.closeButton}>×</Text>
</TouchableOpacity>
</View>
{selectedSequence && results && (
<ScrollView style={styles.modalBody}>
<View style={styles.resultSection}>
<Text style={styles.sectionTitle}>原始序列</Text>
<View style={styles.sequenceDisplay}>
<Text style={styles.sequenceDisplayText}>
[{selectedSequence.data.join(', ')}]
</Text>
</View>
</View>
<View style={styles.algorithmComparison}>
<View style={styles.algorithmCard}>
<Text style={styles.algorithmTitle}>动态规划方法</Text>
<Text style={styles.algorithmComplexity}>时间复杂度: O(n²)</Text>
<View style={styles.resultRow}>
<Text style={styles.resultLabel}>LDS长度:</Text>
<Text style={styles.resultValue}>{results.dp.length}</Text>
</View>
<View style={styles.resultRow}>
<Text style={styles.resultLabel}>LDS序列:</Text>
<Text style={styles.resultValue}>[{results.dp.sequence.join(', ')}]</Text>
</View>
</View>
<View style={styles.algorithmCard}>
<Text style={styles.algorithmTitle}>二分查找优化</Text>
<Text style={styles.algorithmComplexity}>时间复杂度: O(n log n)</Text>
<View style={styles.resultRow}>
<Text style={styles.resultLabel}>LDS长度:</Text>
<Text style={styles.resultValue}>{results.binary.length}</Text>
</View>
<View style={styles.resultRow}>
<Text style={styles.resultLabel}>LDS序列:</Text>
<Text style={styles.resultValue}>[{results.binary.sequence.join(', ')}]</Text>
</View>
</View>
</View>
<View style={styles.conclusionSection}>
<Text style={styles.conclusionTitle}>结论</Text>
<Text style={styles.conclusionText}>
两种算法得出的LDS长度相同,均为 {results.dp.length}。
二分查找优化方法在大数据集上性能更优。
</Text>
</View>
</ScrollView>
)}
</View>
</View>
</Modal>
{/* 算法说明模态框 */}
<Modal
animationType="slide"
transparent={true}
visible={infoModalVisible}
onRequestClose={() => setInfoModalVisible(false)}
>
<View style={styles.modalOverlay}>
<View style={styles.infoModalContent}>
<View style={styles.modalHeader}>
<Text style={styles.modalTitle}>LDS算法说明</Text>
<TouchableOpacity onPress={() => setInfoModalVisible(false)}>
<Text style={styles.closeButton}>×</Text>
</TouchableOpacity>
</View>
<ScrollView style={styles.infoModalBody}>
<Text style={styles.infoTitle}>最长递减子序列 (LDS)</Text>
<Text style={styles.infoText}>
最长递减子序列问题是寻找给定序列中最长的子序列,
使得子序列的元素按降序排列。
</Text>
<Text style={styles.infoSubtitle}>动态规划方法</Text>
<Text style={styles.infoText}>
• 时间复杂度: O(n²){'\n'}
• 空间复杂度: O(n){'\n'}
• 适用于小规模数据集
</Text>
<Text style={styles.infoSubtitle}>二分查找优化方法</Text>
<Text style={styles.infoText}>
• 时间复杂度: O(n log n){'\n'}
• 空间复杂度: O(n){'\n'}
• 适用于大规模数据集
</Text>
<Text style={styles.infoSubtitle}>应用场景</Text>
<Text style={styles.infoText}>
• 算法竞赛{'\n'}
• 数据分析{'\n'}
• 序列比较{'\n'}
• 生物信息学
</Text>
</ScrollView>
</View>
</View>
</Modal>
</SafeAreaView>
);
};
const styles = StyleSheet.create({
container: {
flex: 1,
backgroundColor: '#f0f9ff',
},
header: {
paddingTop: 30,
paddingBottom: 20,
paddingHorizontal: 20,
backgroundColor: '#ffffff',
borderBottomWidth: 1,
borderBottomColor: '#e0f2fe',
flexDirection: 'row',
justifyContent: 'space-between',
alignItems: 'center',
},
title: {
fontSize: 24,
fontWeight: 'bold',
color: '#0c4a6e',
},
subtitle: {
fontSize: 14,
color: '#0369a1',
marginTop: 4,
},
infoButton: {
width: 36,
height: 36,
borderRadius: 18,
backgroundColor: '#e0f2fe',
alignItems: 'center',
justifyContent: 'center',
},
infoIcon: {
fontSize: 20,
color: '#0369a1',
},
content: {
padding: 16,
},
sequenceList: {
// Sequence list styles
},
sequenceCard: {
backgroundColor: '#ffffff',
borderRadius: 16,
padding: 20,
marginBottom: 16,
elevation: 4,
shadowColor: '#000',
shadowOffset: { width: 0, height: 2 },
shadowOpacity: 0.1,
shadowRadius: 8,
},
sequenceHeader: {
flexDirection: 'row',
justifyContent: 'space-between',
alignItems: 'center',
marginBottom: 15,
},
sequenceName: {
fontSize: 18,
fontWeight: 'bold',
color: '#0c4a6e',
},
sequenceLength: {
fontSize: 14,
color: '#0369a1',
},
sequenceData: {
backgroundColor: '#f0f9ff',
borderRadius: 10,
padding: 12,
marginBottom: 15,
},
sequenceText: {
fontSize: 14,
color: '#0284c7',
textAlign: 'center',
},
runButton: {
flexDirection: 'row',
alignItems: 'center',
justifyContent: 'center',
backgroundColor: '#0ea5e9',
paddingVertical: 12,
borderRadius: 12,
},
playIcon: {
fontSize: 18,
color: '#ffffff',
marginRight: 8,
},
runButtonText: {
fontSize: 16,
fontWeight: 'bold',
color: '#ffffff',
},
modalOverlay: {
flex: 1,
backgroundColor: 'rgba(0, 0, 0, 0.5)',
justifyContent: 'center',
alignItems: 'center',
},
modalContent: {
backgroundColor: '#ffffff',
width: '90%',
height: '80%',
borderRadius: 20,
overflow: 'hidden',
},
infoModalContent: {
backgroundColor: '#ffffff',
width: '90%',
height: '70%',
borderRadius: 20,
overflow: 'hidden',
},
modalHeader: {
flexDirection: 'row',
justifyContent: 'space-between',
alignItems: 'center',
padding: 20,
borderBottomWidth: 1,
borderBottomColor: '#e0f2fe',
backgroundColor: '#f0f9ff',
},
modalTitle: {
fontSize: 20,
fontWeight: 'bold',
color: '#0c4a6e',
},
closeButton: {
fontSize: 30,
color: '#7dd3fc',
fontWeight: '200',
},
modalBody: {
flex: 1,
padding: 20,
},
infoModalBody: {
flex: 1,
padding: 20,
},
resultSection: {
marginBottom: 20,
},
sectionTitle: {
fontSize: 18,
fontWeight: 'bold',
color: '#0c4a6e',
marginBottom: 10,
},
sequenceDisplay: {
backgroundColor: '#f0f9ff',
borderRadius: 10,
padding: 15,
},
sequenceDisplayText: {
fontSize: 16,
color: '#0284c7',
textAlign: 'center',
},
algorithmComparison: {
flexDirection: 'row',
justifyContent: 'space-between',
marginBottom: 20,
},
algorithmCard: {
width: '48%',
backgroundColor: '#f0f9ff',
borderRadius: 12,
padding: 15,
},
algorithmTitle: {
fontSize: 16,
fontWeight: 'bold',
color: '#0c4a6e',
marginBottom: 5,
},
algorithmComplexity: {
fontSize: 12,
color: '#0369a1',
marginBottom: 10,
},
resultRow: {
marginBottom: 8,
},
resultLabel: {
fontSize: 14,
color: '#0369a1',
fontWeight: '600',
},
resultValue: {
fontSize: 14,
color: '#0284c7',
fontWeight: 'bold',
},
conclusionSection: {
backgroundColor: '#e0f2fe',
borderRadius: 12,
padding: 15,
},
conclusionTitle: {
fontSize: 16,
fontWeight: 'bold',
color: '#0c4a6e',
marginBottom: 8,
},
conclusionText: {
fontSize: 14,
color: '#0369a1',
lineHeight: 20,
},
infoTitle: {
fontSize: 20,
fontWeight: 'bold',
color: '#0c4a6e',
marginBottom: 15,
textAlign: 'center',
},
infoText: {
fontSize: 15,
color: '#0369a1',
lineHeight: 22,
marginBottom: 15,
},
infoSubtitle: {
fontSize: 17,
fontWeight: 'bold',
color: '#0c4a6e',
marginBottom: 10,
},
svgIcon: {
fontFamily: 'Arial',
},
});
export default LDSComparison;
这段代码实现了一个最长递减子序列(LDS)算法对比分析工具,采用React Native框架开发并深度适配鸿蒙系统。其核心原理基于两种经典LDS算法:动态规划方法通过构建状态转移表记录每个位置的最长递减子序列长度,时间复杂度为O(n²);二分查找优化方法通过维护一个递减的尾部元素数组,利用二分查找快速定位插入位置,时间复杂度优化至O(n log n)。
在鸿蒙生态适配方面,代码充分利用了鸿蒙系统的分布式能力和ArkUI框架特性。通过React Native与鸿蒙原生能力的深度融合,应用能够调用鸿蒙系统级UI组件和性能优化机制。代码中使用的SafeAreaView、ScrollView、Modal等组件在鸿蒙环境下会自动映射为对应的ArkUI组件,确保在鸿蒙设备上获得原生级的渲染性能和用户体验。同时,鸿蒙系统的多设备协同能力使得该应用可以无缝运行在手机、平板、智能穿戴等多种终端设备上,体现了鸿蒙一次开发多端部署的核心理念。

算法实现层面,动态规划方法通过双重循环遍历数组,对于每个元素检查其前面所有元素,当发现递减关系且能形成更长子序列时就更新状态表和前驱指针。这种方法虽然直观易懂,但在处理大规模数据时性能表现较差。二分查找优化方法则采用贪心策略,维护一个递减序列的尾部元素数组,通过二分查找快速确定当前元素在最优解中的位置,避免了不必要的重复计算。这种优化思想体现了算法设计中时间复杂度优化的精髓,通过数据结构的巧妙运用实现性能提升。
用户交互设计充分考虑了鸿蒙系统的UI设计规范和交互习惯。模态框采用鸿蒙标准的滑入动画效果,信息提示面板遵循鸿蒙Material Design设计语言。状态管理机制通过React Hooks实现响应式数据流,确保UI与数据的实时同步。SVG图标系统通过Base64编码处理,这种设计在鸿蒙环境下能够避免图片资源加载问题,提高应用启动速度和运行稳定性。测试数据集涵盖了递减序列、递增序列、随机序列等多种典型场景,为算法验证提供了全面的测试用例。
整体架构采用组件化设计理念,将算法逻辑、UI渲染和状态管理进行解耦,这种设计模式在鸿蒙开发中具有重要意义。鸿蒙系统推荐的组件化开发方式能够提高代码复用率,降低维护成本,同时便于团队协作开发。代码通过TypeScript强类型系统提升了开发效率和代码质量,在鸿蒙DevEco Studio开发环境中能够获得完整的类型检查和智能提示支持,为开发者提供了良好的开发体验。
打包
接下来通过打包命令npn run harmony将reactNative的代码打包成为bundle,这样可以进行在开源鸿蒙OpenHarmony中进行使用。

打包之后再将打包后的鸿蒙OpenHarmony文件拷贝到鸿蒙的DevEco-Studio工程目录去:

最后运行效果图如下显示:

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