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Java Solution for LeetCode algorithm problems, continually updating
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package g0601_0700.s0611_valid_triangle_number;
// #Medium #Array #Sorting #Greedy #Binary_Search #Two_Pointers #Binary_Search_II_Day_1
// #2022_03_21_Time_10_ms_(100.00%)_Space_45_MB_(5.06%)
public class Solution {
public int triangleNumber(int[] nums) {
int n;
int max = 0;
int[] count = new int[1001];
for (int i : nums) {
count[i]++;
max = Math.max(max, i);
}
count[0] = 0;
int idx = 0;
for (int i = 1; i <= max; ++i) {
for (int j = 0; j < count[i]; ++j, ++idx) {
nums[idx] = i;
}
count[i] += count[i - 1];
}
n = idx;
int r = 0;
for (int i = 0; i < n - 2; ++i) {
for (int j = i + 1; j < n - 1; ++j) {
if (nums[i] + nums[j] > max) {
r += (n - j) * (n - j - 1) / 2;
break;
}
r += count[nums[i] + nums[j] - 1] - j - 1;
}
}
return r;
}
}